In oil and gas exploration and development operations, a wellbore may have a casing installed to, for example, provide structural integrity to the wellbore, or to isolate the interior wellbore from the surrounding formation. For later slot recovery, sidetracking, abandonment, and other operations, portions of the casing may be removed. Casing removal may be performed by cutting the casing and pulling the cut casing to the surface to remove the severed portion.
In the example of slot recovery, a new well may be constructed with new barriers from a previously used slot while shutting off communication with an old reservoir. Cutting and pulling casing may be restricted due to cement behind production casing or barite settling from drilling fluid in the production casing annulus. Such slot recovery operations may thus result in the cutting and removal of multiple sections of casing from a wellbore. Because slot recovery operations often involve cutting a casing segment in a first trip and pulling the cut casing in a second trip, such operations are often time consuming and expensive.
Certain apparatus and techniques for extraction of well casing use multiple trips to move cutting and extracting equipment downhole. For instance, in removal operations, a cutting device is first lowered into the wellbore to cut the casing at a desired depth. After performing the cutting operation, the cutting device is returned to the surface. A spearing device is then lowered into the wellbore and engaged with the free end of the casing. Once the free end of the casing is engaged, an attempt is then made to recover the casing by pulling, or, in the case where jars are used, by a combination of pulling and jarring. If these attempts to remove the casing are unsuccessful, the spear assembly is removed from the wellbore and the cutting device is reattached to the tool string, lowered into the wellbore, and used to sever the casing at a point above the original cut. The pulling/jarring process is then repeated until the casing is recovered.
Even when casing is retrieved without performing a second cut of the casing, at least two trips are used to complete a cutting and retrieval operation on account of the utilization of separate cutting and extraction tools. When an extended length of casing is extracted, considerable rig time is also used to move the tools downhole to the site of the cut. Time and expense are therefore increased when multiple cuts are performed to retrieve the casing.